Didymodon contains some 120 species exhibiting a worldwide distribution with primary diversification in the temperate regions and tropical highlands; about 20 species in the Neotropics (many more names than taxa). Low to high open montane, páramo and puna, not uncommon in disturbed sites in the tropical Andes; on soil and rock. This genus, along with Barbula for which many species were previously associated (see discussion under Barbula for comparison between the two genera), are currently being revised by Jiménez (MUB) for South America. The present concept includes Trichostomopsis, cf. Jiménez et al. (2005). The keys recently published by Jiménez and Cano (2008a) are useful for most of the tropical Andes.